[Core][Make] Fixing some small changes for building with OCCA's latest main

[noelchalmers]

Some small tweaks to the build system here.

• No longer hijacking OCCA's makefile in our build. We don't need anything set in there.
• Linking libocca.so via rpath (which means no more needing LD_LIBRARY_PATH !)
• Removing setting occa::env::OCCA_MEM_BYTE_ALIGN. This can now be set directly, outside of the build system.

[tcew]

Nice!

[codecov]

Codecov Report

Merging #66 (1e6c5cf) into master (eb1dcf5) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
- Coverage   84.08%   84.08%   -0.01%     
==========================================
  Files         257      257              
  Lines       20316    20315       -1     
==========================================
- Hits        17083    17082       -1     
  Misses       3233     3233              

Impacted Files	Coverage Δ
libs/core/platformDeviceConfig.cpp	44.44% <ø> (-1.51%)	⬇️

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